(1) Field of the Invention
This invention relates to vessels or cells for sampling liquified gasses and more particularly to pre-charged cells for sampling liquified petroeum gasses (LPG).
(2) Description of the Prior Art
As gasses and particularly liquified petroleum gasses, are produced from deep wells and move into pipe lines in the normal course of commerce, it is desired to obtain periodic samples of the gasses for commercial purposes. Equipment for periodically removing samples from a pipe and introducing it in a pre-charged cell are well-known to the industries. For example, see the following U.S. patents.
McKinney et al.--U.S. Pat. No. 2,636,387 PA1 Rosenwald--U.S. Pat. No. 3,789,670 PA1 Rosenwald--U.S. Pat. No. 3,793,888
As seen by these examples of the prior art, the vessels or cells in which the samples are taken, typically have a cylindrical tube with a sample end and a charge end with a free-floating piston between. The collected liquified gasses will be under considerable pressure. Because the samples are taken over a period of time, there is considerable concern that the different samples of different composition might stratify, so that when a portion of the contents of the cell is removed, a particular stratum would be removed and this would not be a true representation of the total contents of the cell.
Different mixing devices hve been proposed. For example, McKinney et al. discloses a mixing device having a series of dashers connected to a shaft, which extends through a packing gland on one end of a container. (McKinney et al. U.S. Pat. No. 2,636,387; also see Rosenwald U.S. Pat. No. 3,793,888)
Further, it has been suggested that a small ball, similar to a marble placed within an aerosol spray paint can, could be placed within the sample chamber. It is understood that it is desirable that the sample chamber have as small as possible volume when the cell is empty (without a sample). Therefore, when the sample is introduced into the cell, there will be no contamination from residual gasses. Therefore, the ball is fitted into hemispherical recesses formed in the sample end and the piston end. The sample end and piston and have correlative shapes to fit together, so there is a minimum volume when the cell is free of the sample.